Positronium rare annihilation experiment with a positron beam-line using permanent magnets

Positronium (Ps) is a bound state of an electron and a positron, which anni hilates into photons. It is a suitable place to study the quantum electrody namics (QED) since strong and weak interactions are negligibly small in the annihilation processes. Our experimental, group has been measuring rare an nihilation processes from Ps using a multi-gamma-ray spectrometer called UN I which consists of 32 NaI(TI) (3 in phi, x 4 in.) scintillation counters. We had detected the 4 gamma and 5 gamma annihilation processes for the firs t time in the world. In the experiment, similar to 200 4-gamma events and o ne 5-gamma event have been collected, respectively, until today. Since thes e processes do not include any lower order of Feynman graphs, we can study alpha(7) and alpha(8) (alpha: fine structure constant) processes almost pur ely, which is unexplored region of the QED higher order processes. We are p lanning to utilize a positron beam line using permanent magnets. By employi ng EGS4 code system for simulating electromagnetic processes and Runge-Kutt a method for solving equations of motion, detection efficiency of our detec tor and transport efficiency of the beam line have been simulated. (C) 1999 published by Elsevier Science B.V. All rights reserved.